With the increased awareness of the importance of physical health and aerobic exercise, exercise bicycles have become increasingly popular. In the beginning these bicycles were basically stationary versions of an ordinary two wheel bicycle; that is, the user would operate a pair pedals to rotate a loaded wheel not in contact with the ground. These basic machines have the disadvantage of only exercising muscles of the legs or lower torso of the user.
More recently, bicycle exercising machine were developed to exercise muscle groups in the upper part of the body. Two examples are provided in U.S. Pat. Nos. 4,188,030 and 4,657,244. Basically speaking, they are an improvement over U.S. Pat. No. 326,247. In the '247 patent, two sets of pivot arms were operated by the legs and forearms of the user and the arms were linked by an eccentric to drive a flywheel The linkage required that the human legs and arms move together in synchronism. Thus, both the upper and lower body muscle groups had to be exercised at the same time. This is a decided disadvantage to those users who would like to develop one muscle group in preference to the other. One embodiment of the '244 patent allows the pedals to be disengaged so that the arms can be exercised alone. However, because of the number of gears and chain drives, all embodiments of the '244 patent are relatively noisy. Moreover, the nature of the eccentric is not conducive to smooth operation.
What is needed is a smooth running exercising machine which can be used at the option of the user to exercise the muscles of the upper body or the muscles of the lower body or both the muscles of the upper and lower body. Preferably, such an exercising machine should be quiet, smooth running, easy to use, and simple to assemble or trouble shoot. It should also be one which would not inconvenience the user by moving parts of user's body which are not being exercised.